Lucky was grazing in a field Friday afternoon when she walked onto a wooden platform covering a well, The Denver Post reported.
The 1,200- to 1,500-pound cow was too heavy for the structure and fell through, said Laura McConnell, spokeswoman for Mountain View Fire Rescue.
Firefighters, animal control officers and neighbors showed up on the scene at 3:30 p.m.
One neighbor climbed down into the well to calm the cow, said Mountain View Lt. Tim Losh. The neighbor also called someone who owned a crane.
Firefighters attached a fire hose to the crane to lift the animal out of the well.
Lucky was very calm as she was hoisted out of the well.
"It was a pretty docile cow. Basically she let us do what we wanted to do," Losh told the Post. "I didn't notice any injuries."
A veterinarian examined Lucky afterward, McConnell said, adding the cow is doing fine.